1. Field of the Invention
The present invention relates to a method for accessing content in networks, preferably in wide area networks, a corresponding system and uses of the method and/or the system.
2. Description of the Related Art
Content delivery networks (CDNs) are used to store content and to provide or give access to that content for a user. The content delivery networks are usually connected to the Internet and provide for example mirrored content on different proxy servers preferably in different locations worldwide. For example a company having branches in different countries or at least on different continents provides regional adapted software-updates on proxies or servers mirroring or caching the software-update which are each located on the different continents. A user may request the software-update of company abcde for download in a version 1.0 by specifying a resource identifier for example in form of a hostname www.abcde.de/software-update/V1. The hostname is then usually transmitted to a server for resolving a unique hosting server identifier corresponding to the hostname, so that a client may download the software-update.
To provide a most suitable download of the software-update for a user, the location of the user may be taken into account when resolving the hosting server identifier in form of an IP-address: If a user for example is located in Germany the IP-address to the German proxy server or European proxy server is provided for the hostname otherwise smaller data transfer rates and unnecessary traffic is produced: If the IP-address of a proxy server in China hosting the software-update were to be provided to the user located in Germany the data transfer rate would be smaller compared to the data transfer rate of a German proxy server due to the “bottleneck” of interconnection points of the Internet.
The current content delivery networks are usually based on domain name resolution of hostnames via DNS to point a user to a most suitable server for accessing or download requested content: For example when the company has a plurality of proxy servers each hosting or mirroring the content, these proxies are all assigned to the hostname by specifying DNS aliases, so-called CNAMES, to the public resource name respectively the hostname. Each CNAME corresponds to one proxy server of the content delivery network.
When a user therefore requests www.abcde.de/software-update/V1 the user location may taken into account by a cache selection logic via the IP-address from which the DNS request, i.e. the request for accessing www.abcde.de/software-update/V1, was transmitted.
The domain name system is structured hierarchically, i.e. that virtual higher layers of the hierarchy “see” only the IP-address of the requesting or handling DNS server but not for example the client's IP address. That might result in a non-optimal IP-address resolving for the user: If the user located in Germany requests www.abcde.de/software-update/V1 a DNS-server for example located in France is requested for resolving the IP-address for the requested hostname. The DNS-server then tries to resolve the IP-address for the specified hostname. However the DNS-server might have to contact a CDN-DNS-server in Spain of a content delivery network for resolving the IP-address. The CDN-DNS-Server receives the specified hostname to be resolved and the IP-address of the DNS-server but not the IP-address of the client. The IP-address of the most suitable server according to a cache selection logic is then a proxy server in France hosting the requested content. The client receives via the DNS-server the IP-address of a proxy in France for the hostname www.abcde.de/software-update/V1. However a proxy server in Germany would have been more suitable for download usually providing higher data transfer rates.
Since there exist a variety of free and popular DNS-servers, located worldwide this adds to the above mentioned non-optimal selection of proxies.
To overcome this drawback it was proposed to modify the DNS protocol for resolving IP-addresses of hostnames by adding the client's IP-address to the DNS-protocol, respectively the initial IP-address of the IP-resolving request, or by adding at least a sub-network identification information to allow identification of the region of the user to enhance IP-address resolution and enhanced guiding of the user to a more suitable server for download.
These modifications are however cost-intensive, since all DNS-servers have to be provided with such a modification. If in the whole chain of IP-address resolving requests only one DNS-server is not equipped with the above-mentioned modification of the DNS protocol the information about the client's IP address is lost for the other DNS-servers leading again to non-optimal resolution of the IP-address.
Another problem is privacy protection of the user: If the client's user IP-address is transmitted for determining the location of the user, this enables potential sniffers or attackers to contact directly the user's computer and to try to access personal data of the user like passwords, documents, emails or the like.